Depression and anxiety are caused by numerous factors, including conscious fears, subconscious fears, and stress. They are debilitating conditions that can severely affect an individual. For example, chronic anxiety impairs serotonin synapse uptake and depletes adrenal glands. As another example, stress lowers opioid levels in an individual, causing a sense of urgency, irritability, and depression. Regulating neurotransmitters in the brain is viewed as an important way to treat depression and anxiety.
Combinations of drugs are commonly used to treat life-threatening diseases such as HIV and various cancers. However, this approach has not been commonly adopted to treat less serious disorders in part because of possible side effects.